This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. We describe a simple tandem mass spectrometric approach toward structural characterization of mycolic acids, the long-chain [unreadable]-alkyl-[unreadable]-hydroxy fatty acids unique to mycobacteria and related taxa.